1. Field of the Invention
This invention relates to a device for controlling an internal combustion engine during deceleration.
2. Description of the Prior Art
In a vehicular internal combustion engine, when the throttle valve is closed to decelerate the vehicle or the engine, a strong vacuum develops in the air intake passage or intake manifold downstream of the throttle valve. The vacuum causes a few problems, such as an increase in the consumption of engine lubricant. Accordingly, a vacuum control device is sometimes provided to supply air to the air intake passage downstream of the throttle valve to prevent the development of an excessively strong vacuum at that position.
Some engines have fuel-supply cut-off devices for the purpose of fuel economy. The cut-off device interrupts fuel supply to the engine during deceleration under certain predetermined conditions.
In the case of an engine equipped with both a vacuum control device and a fuel-supply cut-off device, when the engine rotational speed (rpm) decreases to a range at which fuel supply is recommenced or recovered, the vacuum control device usually continues to perform its air supply function. At such a time, there is therefore a chance that the supplied fuel will mix with an excessive amount of air to form an unduly lean air-fuel mixture, which is supplied to the engine.